I Field of the Invention
The present invention relates to new polymeric products of high purity whose molecules consist essentially of carbon, fluorine, and oxygen and having a polyether structure and to a new process for preparing the same by directly fluorinating the corresponding polyether consisting essentially of carbon, hydrogen, and oxygen in a solvent. More particularly, the present invention relates to perfluorinated polyethers consisting of about one to eleven --(CF.sub.2 CF.sub.2 O) repeating units terminated with perfluorinated C.sub.1 -C.sub.5 alkyl radicals and to a new process for preparing the same by directly fluorinating the corresponding polyether in an inert solvent.
II Description of the Prior Art
Certain organofluoro compounds and polymers are known to exhibit outstanding high temperature stability properties and chemical inertness. Organofluoro compounds containing only carbon and fluorine atoms, fluorocarbon ethers and fluorocarbon amines are three general classes of materials which have found commercial success as coolants, lubricants, heat-transfer agents in reflow condensation soldering processes, and other functional fluid uses. Many compounds can be fully and directly chlorinated or brominated. However, when such compounds are directly fluorinated considerable difficulties are encountered.
Because perfluorinated polyethers have desirable properties, such as extremely good heat stability, outstanding chemical inertness, excellent lubricating properties and the like, much effort has been made to prepare perfluorinated polyethylene oxide having perfluoroalkyl terminal groups. Limited success has been reported in preparing such perfluorinated polymers having a low number (i.e., 2-4) of repeating ethylene oxide units and in preparing such perfluorinated polymers having a high molecular weight. For example, when high molecular polyethylene oxides are perfluorinated, most of the resulting product is a high molecular weight solid with only a small amount of low molecular weight fluid being formed. In order to prepare perfluorinated polyethers of mid-range molecular weights, i.e. being composed of 4-11 perfluoroethylene oxide units, it has been suggested to break solid perfluoro polyethers of high molecular weight into low molecular weight fragments by means of pyrolyzing the perfluoro polyethers at extremely high temperatures of 500-600.degree. C. and collecting the vaporized lower molecular weight perfluoro polyether fluids. The pyrolysis is not only expensive and difficult to carry out but also the resulting fluids are random mixtures of many perfluoro polyethers because of the random nature of the bond breakage of the high molecular weight perfluoro polyethers. The fragments must be reacted with fluorine gas to eliminate acyl end groups and any unsaturation of the resulting perfluoro polyethers.
Efforts to provide a process for the direct fluorination of organic compounds in solvents have heretofore been fraught with many problems, including the breakdown of the solvent by the fluorine gas, formation of explosive mixtures, and the insolubility of the fluorine gas with the solvent.